1. Field of the Invention
The present invention relates to a wideband monopole antenna, and more particularly to a wideband monopole antenna having a feeder unit bent at a predetermined angle.
2. Description of the Related Art
Portable communication apparatuses, such as HHPs, CT-2 cellular phones, smart phones, digital phones, PCS phones, PDAs, and laptop computers, are becoming smaller and have multi-functionality. In addition to voice communication and radio listening capabilities, they are now equipped to access the Internet and download MP3 music clips. Various information and images in the form of digitalized data can be also easily accessed using portable devices. Such information is band-compressed using audio or video technology and can be easily and effectively transmitted via digital radio communication or digital radio broadcasting.
Current technological trend demands a rapid increase in new services which require a larger capacity and more bandwidths. As a result, the cost associated with the provision of new base stations and repeaters to accommodate modem devices is increasing. One way to accommodate the new demand is to provide a wideband antenna satisfying a bandwidth of 0.7 GHz-2.5 GHz. A typical example of a multiple wideband antenna is a UWB (ultra-wideband) antenna.
In using multiple UWB antenna, the most critical issues relate to improving the antenna efficiency and reducing an electromagnetic absorption ratio. The UWB antennas usually use pulses having a width of 1 nsec or less to transmit information, instead of RF carrier waves. Since a power spectrum as low as baseband noise exists over a wide band due to the property of the pulses, the UWB antennas can perform transmission without any interference from other radio communication systems currently being used. Further, they have a wider bandwidth and a larger transmission speed than the conventional antennas.
Moreover, the UWB antennas using very short pulses can distinguish both signals even when there is a difference in the path reaching between the direct and reflected waves. As such, they are suitable for use in multiple paths and able to obtain an accuracy in the unit of cm using the resolution of short pulses. They have excellent obstacle penetration characteristics due to wideband characteristics, thus can be easily integrated as inground penetration radars and position tracking systems. However, the UWB antennas must be compact and light to be mounted on the terminals, while meeting the performances required as expected in the UWB systems.
FIGS. 1 and 2 show a conventional monopole antenna. As shown, a monopole antenna 3 is provided with a Y-type feeder line 4 on the rear surface of a substrate 1, which is provided with a ground surface 2, and electrically connected to a connection unit 3a of the antenna. The substrate 1 has an antenna connector 5 connected to the Y-type feeder line 4.
When the monopole antenna has a Y-type feeder line on the rear surface of the substrate, however, the substrate 1 and the radiator must be enlarged to accommodate the size of the feeder line, thus increasing the overall size of the antenna.
In addition, the Y-type feeder line is typically made of a flexible wire and has no support force. When the contour of the antenna vibrates severely due to an external impact (e.g., wind or shock), the contact portion of the feeder line vibrates together. As a result, the radiation characteristics and matching band of the antenna can be easily varied and the function of the antenna may deteriorate. However, if the feeder portion is shortened to reduce the size of the antenna, the bandwidth decreases.